Development of NbTiB Microalloyed HSLA Steels for High-Strength Heavy Plate

2005 ◽  
Vol 500-501 ◽  
pp. 565-572 ◽  
Author(s):  
H. Meuser ◽  
F. Grimpe ◽  
S. Meimeth ◽  
C.J. Heckmann ◽  
C. Träger
Keyword(s):  
High Strength ◽  
Optimum Process ◽  
Low Carbon ◽  
Low Alloy Steel ◽  
Alloying Element ◽  
Heavy Plate ◽  
Hsla Steels ◽  
Bainitic Microstructure ◽  
Bainitic Structure ◽  
Low Temperature Toughness

This paper deals with the development of low carbon NbTiB micro-alloyed high strength low alloy steel for heavy plates with high wall thickness. In the production of heavy plate it is remarkably difficult to achieve a combination of high strength and good low-temperature toughness. Bainitic microstructures have shown the capability to attain such requirements. To achieve a bainitic microstructure even for heavy wall products the formation of bainite can be promoted and supported by the use of small amounts of boron as a micro-alloying element. This industrial research project is based on the addition of small amounts of boron to promote the desired bainitic structure. Mill rolling trials were carried out to determine the optimum process parameters. The results of experimental mill rolling trials on 35 mm plates will be presented in this paper.

ULTRA-FORM 80

Alloy Digest ◽  
1973 ◽  
Vol 22 (7) ◽  
Keyword(s):  
High Strength ◽  
Heat Treating ◽  
Low Carbon ◽  
Low Alloy Steel ◽  
Bethlehem Steel Corporation ◽  
Temperature Performance ◽  
Inclusion Shape ◽  
Ferrite Grain Size ◽  
Minimum Yield ◽  
Shape And Size

Abstract Ultra-Form 80 is a low-alloy steel developed for its combination of high strength, good formability, fatigue resistance, toughness and weldability. It has a minimum yield strength of 80,000 psi and is characterized by its low carbon and alloy content, very fine ferrite grain size, and controlled inclusion shape and size. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness and fatigue. It also includes information on low and high temperature performance, and corrosion resistance as well as forming, heat treating, joining, and surface treatment. Filing Code: SA-291. Producer or source: Bethlehem Steel Corporation.

FIB and TEM Studies on the Bainitic Microstructure in Low Carbon HSLA Steels

2007 ◽  
Vol 26-28 ◽  
pp. 73-76 ◽  
Author(s):  
J.S. Kang ◽  
S.S. Ahn ◽  
C.Y. Yoo ◽  
Chan Gyung Park
Keyword(s):  
Acicular Ferrite ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Bainitic Ferrite ◽  
Granular Bainite ◽  
Low Carbon ◽  
3 Dimensional ◽  
Hsla Steels ◽  
Bainitic Microstructure ◽  
Lath Structure

In the present study, focused ion beam (FIB) technique was applied to make site-specific TEM specimens and to identify the 3-dimensional grain morphologies of bainitic microstructure in low carbon HSLA steels such as granular bainite, acicular ferrite and bainitic ferrite. Granular bainite consisted of fine subgrains and 2nd phase constituents like M/A or pearlite located at grain and subgrain boundaries. Acicular ferrite was characterized by an aggregate of ramdomly orientated and irregular shaped grains. The high angle boundaries between adjacent acicular ferrite grains caused by intragranular nucleation during continuous cooling process. Bainitic ferrite revealed uniform and parallel lath structure within the prior austenite grain boundaries and its’ packet size could effectively decreased by the formation of intragranular acicular ferrite.

Development of Low Carbon Microalloyed Ultra High Strength Steels

2005 ◽  
Vol 500-501 ◽  
pp. 551-558 ◽  
Author(s):  
A. Ghosh ◽  
Brajendra Mishra ◽  
Subrata Chatterjee
Keyword(s):  
Room Temperature ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Hsla Steels ◽  
Finish Rolling ◽  
Ultra High Strength Steels ◽  
Rolling Temperatures ◽  
Carbon Microalloyed ◽  
Carbon Concentrations

In the present study HSLA steels of varying carbon concentrations, alloyed with Mn, Ni, Cr, Mo, Cu and micro-alloyed with Nb and Ti were subjected to different finish rolling temperatures from 850oC to 750oC in steps of 50oC. The microstructure of the steel predominantly shows martensite. Fine twins, strain induced precipitates in the martensite lath along with e-Cu precipitates are observed in the microstructure. With an increase in carbon content the strength value increases from 1200MPa UTS to 1700MPa UTS with a negligible reduction in elongation. Impact toughness values of 20-26 joules at room temperature and −40oC were obtained in sub-size samples.

Metallurgical Design of Newly Developed Material for Seamless Pipes of X80–X100 Grades

2007 ◽  
Author(s):  
Yuji Arai ◽  
Kunio Kondo ◽  
Hiroyuki Hirata ◽  
Masahiko Hamada ◽  
Nobuyuki Hisamune ◽  
...  
Keyword(s):  
Oil And Gas ◽  
High Strength ◽  
Medium Size ◽  
Low Carbon ◽  
Seamless Pipe ◽  
Tempering Temperature ◽  
Deep Well ◽  
Oil And Gas Fields ◽  
Bainitic Structure ◽  
Gas Fields

With the increasing development of oil and gas fields in deepwater or ultra-deepwater with deep well depth, the development of high strength seamless pipe has become necessary. This paper describes a metallurgical design of seamless pipe with high strength reaching X80–X100 grade (minimum yield strength, 552 MPa–689 MPa) manufactured by steel containing very low carbon and with a microstructure of uniform bainite. The effect of microstructure of quenched and tempered (QT) steel on strength and toughness is investigated in laboratory. Uniform bainitic structure without coarse martensite-austenite constituent (M-A) is obtained by lowering bainite transformation temperature during quenching process by controlling the alloying elements. Moreover the structure is very effective in obtaining good toughness for tempered steel even with the high strength X100 grade. Sufficiently low hardness and good toughness in heat affected zone (HAZ) are confirmed by welding tests. The trial production of developed steel is conducted by applying inline QT process in medium-size seamless mill according to an alloying design obtained in laboratory tests. The seamless pipes of the trial production achieve grades X80 to X100 by changing tempering temperature. Some data of mechanical properties of the produced pipes is introduced.

Electron Microscope studies of the microstructures in as-quenched and aged HSLA-100 production steels and correlation with mechanical properties

1991 ◽  
Vol 49 ◽  
pp. 582-583
Author(s):  
A.G. Fox ◽  
V.R. Mattes ◽  
S. Mikalac ◽  
M.G. Vassilaros
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Solid Solution Strengthening ◽  
Austenite Grain ◽  
Microstructure And Mechanical Properties ◽  
Hsla Steels ◽  
Carbonitride Precipitation ◽  
Strength And Toughness

Because of their excellent weldability, high strength low alloy (HSLA) ultra low carbon bainitic (ULCB) steels are finding increasing applications in ship and submarine construction. In order to achieve the required strength and toughness in ULCB HSLA steels it is necessary to control chemical composition and thermo-mechanical processing very carefully so that the desired microstructure and mechanical properties can be achieved. For instance HSLA 100 ULCB steel (nominal yield strength 100 ksi) used by the U.S. Navy in shipbuilding applications can derive its strength and toughness from the following sources:- (1) solid solution strengthening (2) small prior austenite grain size derived from niobium carbonitride precipitation at austenite grain boundaries (3) dislocation substructure and (4) from copper precipitates (in aged alloys). The object of the present work is to correlate the microstructure and mechanical properties of production batches of HSLA 100 in the quenched and aged conditions. Because many of the salient features of these microstructures are submicron in size it was found necessary to use SEM and TEM.

Effect of Hot Rolling and Thermal Treatment on the Microstructure Evolution of Microalloyed Bainitic Steels for Pipeline

2017 ◽  
Vol 746 ◽  
pp. 176-183 ◽  
Author(s):  
Alexander Kabanov ◽  
Grzegorz Korpala ◽  
Rudolf Kawalla ◽  
Sergey Ionov
Keyword(s):  
Heat Treatment ◽  
Microstructure Evolution ◽  
High Strength ◽  
Accelerated Cooling ◽  
Experimental Modelling ◽  
Heavy Plate ◽  
Bainitic Steels ◽  
Bainitic Microstructure ◽  
Effect Of Hot Rolling

Heavy plate for pipelines, which are used in earthquake-prone areas, must have among other a good ductility. The ductility is needed to prevent cracking in the case of local plastic deformation. The bainitic steels with retained austenite or martensite meet these requirements. The aim of this investigation is the determination of the thermo-mechanical treatment parameters with which such microstructures can be generated during the heavy plate production or an additional heat treatment. Experimental modelling of the production process for heavy plate was realized on a Gleeble HDS-V40 thermo-mechanical simulator. Moreover, the microstructure evolution processes during cooling on the round out table were investigated by dilatometry. The investigations on the formation of the microstructure during following accelerated cooling and heat treatment combination were carried out. All investigations were realized with two high-strength micro-alloyed steels, one of which was additionally alloyed with molybdenum. Results revealed that the decreasing of the temperature and duration of the heat treatment as well as addition of molybdenum reduce the size of grains and promotes the nucleation of the bainitic microstructure.

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